A type of vehicular rear wheel steering device is disclosed in JP2009-113730A (hereinafter referred to as Patent reference 1). In the vehicular rear wheel steering device disclosed in the Patent reference 1, a first end of a rod is non-turnable with respect to a housing and movably supported in an axial direction at a spline structure of a conversion mechanism, which includes spline protrusions formed on the rod and spline grooves formed on the housing, while a second end of the rod is non-turnable with respect to a housing and movably supported in an axial direction via a predetermined clearance in a radial direction of the rod.
In the vehicular rear wheel steering device disclosed in the Patent reference 1, in addition to the predetermined clearance defined in a radial direction of the rod between the second end of the rod and the housing, another clearance is defined in the radial direction of the rod between the first end and the housing, the clearance that is defined between a spline protrusion and a spline groove. As a result, when the rod moves in the radial direction of the rod with respect to the housing, an abnormal noise may be generated. Removing the aforementioned clearances may prevent a generation of the abnormal noise. In such a case, an operation of the spline structure may be limited and, in addition, the wearing of sliding portions at the ends of the rod between the housing may increase.
A need thus exists for a vehicle seat device, which is not susceptible to the drawback mentioned above.